We propose interactive beautification, a technique for rapid geometric design and introduce the technique and its algorithm with a protoype system Pegasus. The motivation is to solve a problem wih current drawing systems: too may complex commands and unintiutive procedures to satisfy geometric constraints. The ineractive beautification system recieves the user's free stroke and beautifies it by considering geometric constraints among segments. A single stroke is beautified on after another, preventing accumulation of recognition errors or catastrophic deformation.